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Wednesday, January 22, 2014

Vermicompost Opinion Piece

Q. A lot of people are raving about worm castings. What is your opinion?

A. Producing worm castings is a form of composting. Some people add worms to finished compost so the worms do not have to survive the very high temperatures produced during composting.
            Another method is to add worms directly to a fresh compost letting worms mix and digest scraps in the compost heap directly. Either way the resulting product is a very high grade of compost uniform in size and consistency.
            The finished worm compost or vermicompost has a low percentage of nitrogen, phosphorus and potassium among other nutrients as well. The finished product is humus, just like it is in compost.
            Humus has many other benefits such as a lowering of the pH, increase in organic acids that act as natural chelating agents and an increase in biological activity.
            So, in a nutshell, what is there not to like? However, producing vermicompost without composting first may produce a product that has more health concerns and weeds than traditional compost.

            Composting releases nutrients and many other It was first recommended that after traditional composting this compost was taken through a second stage of composting by worms, vermicomposting. Vermicomposting is now done directly with waste products, many times skipping the traditional composting step. Traditional composting done correctly produces temperatures high enough to kill most microorganisms associated with health concerns like E. coli. If temperatures were high enough, it also killed most weed seeds. However, research has shown that both pathogens and weed seeds can be destroyed in vermicomposting. Vermicomposting is usually done in containers and can be done indoors and outdoors, allowing year round composting.
            It takes compost to a different level. There are some good and some not as good. After it passes through the gut of a worm, it is more finely digested and makes nutrients more quickly available to plants making it act more closely to a faster releasing fertilizer. The down side of it, it is not as good at re-building desert soil structure and stimulating microorganisms as compost can be. Below is for your information with my comments inserted in ( ) and important points highlighted.

Effects of composting with earthworm on the chemical and biological properties of agricultural organic wastes: a principal component analysis.

Liu T, Ren ZL, Zhang C, Chen XF, Zhou B, Dai J.

Taking mixed agricultural organic wastes cattle manure and rice straw (C:N = 28.7:1) as the substrate of earthworm Eisenia foetida, an experiment was conducted to study the effects of earthworm on the changes of the chemical and biological properties of wastes during vermi-composting. After 30 days of vermi-composting, the substrate' s pH and C/N decreased (this is good) while the total P content increased significantly, and the total N, available N, dissolved organic carbon, available P content, microbial biomass-C, respiration rate, and microbial quotient increased by 8.5% , 2.6%, 1.8%, 6.3%, 21.2%, 4.4%, and 30.0% (this is also good) whereas the organic matter content (not as good if you are re-building a desert soil) and metabolic quotient (activity of microorganisms) decreased by 5.0% and 21.9%, respectively, as compared with natural composting. Vermi-composting made the substrate have higher invertase, acid phosphatase, and alkaline phosphatase activities but lower catalase and urease activities. Principal component analysis and discriminant analysis confirmed the significant differences in the substrate' s chemical and biological properties between vermi-composting and natural composting. This study indicated that vermi-composting was superior to natural composting, which could obviously improve the chemical and biological properties of composted organic materials, being a high efficient technology for the management of agricultural organic wastes.

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